Rotating fluid machine

ABSTRACT

At a contact point, a spherical projecting portion of a piston presses a spherical recessed portion of a swash plate due to a working medium supplied to an operating chamber. The contact point is located on a cross line, on which a plane including a center of curvature of the spherical recessed portion and an axis Ls of the swash plate intersects the spherical recessed portion. Therefore, even if the piston forcefully presses the swash plate, the spherical projecting portion and the spherical recessed portion at the contact point are prevented from slipping in a circumferential direction, a radial direction and the like. Thus, the phases of a rotor and the swash plate are prevented from being displaced and causing vibration and noise. A large side thrust is prevented from acting on the piston and causing heat due to twisting and sliding friction between the piston and the cylinder.

CROSS-REFERENCE TO RELATED APPLICATION

The present non-provisional application claims priority under 35 USC 119 to Japanese Patent Application No. 2004-8813 filed on Jan. 16, 2004 the entire contents thereof is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotating fluid machine in which a rotary valve controls the supply and discharge of a working medium to and from an operating chamber formed between a piston and a cylinder of an axial piston cylinder group.

2. Description of the Related Art

A rotating fluid machine for controlling the supply and discharge of a working medium to and from an operating chamber is disclosed in Japanese Patent Application Laid-open No. 2002-256805. In this rotating fluid machine, a spherical projecting portion is provided at a tip end of a piston of an axial piston cylinder group disposed in a rotor, to abut against a spherical recessed portion provided at a swash plate. When the piston is pushed out of the cylinder by high-temperature high-pressure steam supplied to the operating chamber, the spherical projecting portion of the piston presses the spherical recessed portion of the swash plate, and the reaction force which the piston receives from the swash plate provides a rotational torque to the rotor.

If the high-temperature high-pressure steam is supplied to the operating chamber at the time of the start of an intake stroke to abruptly build up the pressure in the operating chamber so that the piston is forcefully pushed out, the contact surface pressure between the spherical projecting portion of the piston and the spherical recessed portion of the swash plate abruptly rises, leading to a possibility that the contact point between the spherical projecting portion and the spherical recessed portion slips in the circumferential direction, the radial direction and the like of the swash plate. When the contact point between the spherical projecting portion and the spherical recessed portion slips, the phases of the rotor and the swash plate change and the rotational angular speed of the rotor suddenly changes to cause vibration and noise. Moreover, a large side thrust acts on the piston and heat due to a twisting and sliding friction that occurs between the piston and the cylinder, causing abnormal friction and seizure.

SUMMARY OF THE INVENTION

The present invention has been achieved in view of the above circumstances, and has its object to prevent slip of a contact point between a spherical projecting portion of a piston and a spherical recessed portion of a swash plate of a rotating fluid machine.

In order to attain the above-described object, according to a first feature of the present invention, there is provided a rotating fluid machine with a casing, a rotor rotatably supported by the casing and an axial piston cylinder group annularly disposed in the rotor to surround an axis of the rotor. A swash plate is provided that is rotatably supported on an axis inclined with respect to the axis of the rotor with a rotary valve which controls the supply and discharge of a working medium to and from an operating chamber formed between a piston and a cylinder of the axial piston cylinder group. A spherical projecting portion is formed at a tip end of the piston abutting against a spherical recessed portion that is annularly disposed in the swash plate to surround the axis of the swash plate. The rotor is rotationally driven by a reaction force which the spherical projecting portion of the piston receives from the spherical recessed portion of the swash plate with the piston advancing by pressure of the working medium supplied to the operating chamber. A contact point at which the spherical projecting portion of the piston presses the spherical recessed portion of the swash plate is located on a cross line on which a plane including a center of curvature of the spherical recessed portion and the axis of the swash plate intersects the spherical recessed portion.

According to a second feature of the present invention, the contact point at a moment when the working medium is supplied to the operating chamber is located on the cross line.

According to a third aspect of the invention, the working medium is a compressible fluid.

With the arrangement of the first feature, the contact point of the spherical projecting portion of the piston presses the spherical recessed portion of the swash plate that is located on the cross line on which the plane including the center of curvature of the spherical recessed portion and the axis of the swash plate intersects the spherical recessed portion. Therefore, even if the piston forcefully presses the swash plate, the spherical projecting portion and the spherical recessed portion at the contact point are prevented from slipping in the circumferential direction, the radial direction and the like, and the phases of the rotor and the swash plate are prevented from being displaced to cause vibration, noise, and abnormal abrasion and seizure due to slide friction and heat generation, and the like.

With the arrangement of the second feature, the contact point at the moment when the working medium is supplied to the operating chamber is located on the cross line, and therefore at the moment when the pressure of the operating chamber abruptly rises, namely, when the spherical projecting portion of the piston and the spherical recessed portion of the swash plate are most likely to slip at the contact point, the slip is reliably prevented to provide smooth rotation of the rotor.

With the arrangement of the third feature, the working medium is a compressible fluid. Therefore, even if the pressure impulsively rises at the moment when the working medium is supplied to the operating chamber, the spherical projecting portion and the spherical recessed portion at the contact point are prevented from slipping, to thereby ensure smooth rotation of the rotor.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a longitudinal sectional view of an expander;

FIG. 2 is an enlarged view of the section 2 in FIG. 1 (sectional view taken along the line 2-2 in FIG. 6);

FIG. 3 is an exploded perspective view of a rotor;

FIG. 4 is a view seen along the arrowed line 4-4 in FIG. 2;

FIG. 5 is a graph showing pressure fluctuation of an operating chamber with respect to a rotational angle of the rotor;

FIG. 6 is a view seen along the line 6-6 in FIG. 2;

FIGS. 7A and 7B are views showing loci of contact points of five pistons; and

FIG. 8 is a view corresponding to FIG. 4, according to a second embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1 to FIG. 3, an expander E of this embodiment is used in, for example, a Rankine cycle system. The expander E converts the thermal energy and the pressure energy of high-temperature high-pressure steam as a working medium into mechanical energy that is outputted. A casing 11 of the expander E is formed from a casing body 12 with a front cover 15 joined via a seal 13 to a front opening of the casing body 12 by a plurality of bolts 14. A rear cover 18 is joined via a seal 16 to a rear opening of the casing body 12 by a plurality of bolts 17, and an oil pan 21 is joined via a seal 19 to a lower opening of the casing body 12 by a plurality of bolts 20.

A rotor 22 is arranged rotatably around an axis Lr and extends in the fore-and-aft direction through the center of the casing 11 with a front part supported by combined angular bearings 23 provided in the front cover 15, and a rear part thereof supported by a radial bearing 24 provided in the casing body 12. A swash plate holder 28 is formed integrally with a rear face of the front cover 15. A swash plate 31 is rotatably supported by the swash plate holder 28 via an angular bearing 30. The axis Ls of the swash plate 31 is inclined relative to the axis Lr of the rotor 22, and the angle of inclination is fixed.

The rotor 22 includes an output shaft 32 supported in the front cover 15 by the combined angular bearings 23 with three sleeve support flanges 33, 34, and 35 formed integrally with a rear part of the output shaft 32. A rotor head 38 is joined by a plurality of bolts 37 to the rear sleeve support flange 35 via a metal gasket 36 and is supported in the casing body 12 by the radial bearing 24. A heat-insulating cover 40 is fitted over the three sleeve support flanges 33, 34, and 35 from the front and joined to the front sleeve support flange 33 by a plurality of bolts 39.

Sets of five sleeve support holes 33 a, 34 a, and 35 a are formed in the three sleeve support flanges 33, 34, and 35 respectively at intervals of 72° around the axis Lr. Five cylinder sleeves 41 are fitted into the sleeve support holes 33 a, 34 a, and 35 a from the rear. A flange 41 a is formed on the rear end of each of the cylinder sleeves 41, and axial positioning is carried out by abutting this flange 41 a against the metal gasket 36 while fitting the flange 41a into a step 35 b formed in the sleeve support holes 35 a of the rear sleeve support flange 35. A piston 42 is slidably fitted in an inside of each of the cylinders 41 with the spherical projecting portion 42 a formed at a tip end of the piston 42 abutting against a spherical recessed portion 31 a formed on the swash plate 31. An operating chamber 43 for steam is defined between the rear end of the piston 42 and the rotor head 38.

As is obvious from FIG. 1, FIG. 2 and FIG. 4, a steam supply pipe 85 is disposed on the axis Lr of the rotor 22, and a steam discharge pipe 89 is disposed eccentrically outwardly in a radial direction of the steam supply pipe 85. A rotary valve 71 includes a fixed side valve plate 73 fixed to the casing 11 and a movable side valve plate 74 fixed to the rotor 22, which slidably abut against each other on a slide surface 77. A first steam passage P1 (see FIG. 1) is formed inside the steam supply pipe 85 and communicates with a circular second steam passage P2 opening to the slide surface 77. An arc-shaped fifth steam passage P5 opening to the slide surface 77 communicates with the steam discharge pipe 89. In the movable side valve plate 74, five third steam passages P3 communicable with the second steam passage P2 and the fifth steam passage P5 on the slide surface 77 are equidistantly disposed to surround the axis Lr. The five third steam passages P3 respectively communicate with five operating chambers 43 via five fourth steam passages P4 which penetrate through the rotor head 38.

As is obvious from FIG. 4, the circular second steam passage P2 (shown by the chain line) and the arc-shaped fifth steam passage P5 (shown by the chain line) formed in the fixed side valve plate 73, and one of the five third steam passages P3 (shown by the solid line) opening to the movable side valve plate 74, open to the slide surface 77 between the fixed side valve plate 73 and the movable side valve plate 74. The rotational direction of the movable side valve plate 74 which rotates with the rotor 22 is shown by the arrow. The third steam passage P3 communicates with the second steam passage P2 at the same time when the third steam passage P3 is shut off from communication with the fifth steam passage P5 at a position P3 (1) with an angle α before the top dead center. The third steam passage P3 is shut off from communication with the second steam passage P2 at a position P3 (2) which is past the top dead center TDC by the angle α, and the intake stroke is performed from the position P3 (1) to the position P3 (2). The third steam passage P3 communicates with the fifth steam passage P5 at a position P3 (3) with an angle β before a bottom dead center BDC. An expansion stroke is performed from the position P3 (2) to the position P3 (3), and an exhaust stroke is performed from the position P3 (3) to the position P3 (1).

FIG. 5 shows the pressure change in the operating chamber 43 with respect to the rotational angle of the rotor 22 with the top dead center as the reference. In the intake stroke which begins from the position with the angle a before the top dead center and finishes at the position past the top dead center by the angle a, the second steam passage P2 communicates with the third steam passage P3 to increase the pressure at a dash. In the subsequent expansion stroke, the high-temperature high-pressure steam expands in the operating chamber 43 which is hermetically sealed, whereby the pressure gradually decreases, so that the high-temperature high-pressure steam becomes the low-temperature low-pressure steam. In the subsequent exhaust stroke, the operating chamber 43 is opened to reduce the pressure, so that the pressure becomes substantially the same pressure as that in the inner pressure of the condenser (substantially the atmospheric pressure).

FIG. 6 is the view of the swash plate 31 seen in a direction of its axis Ls, with the center of curvatures O of five spherical recessed portions 31 a being equidistantly located on a circle with the axis Ls of the swash plate 31 as the center. Meanwhile, the axis Lr of the rotor 22 is inclined by the angle θ with respect to the axis Ls of the swash plate 31, and therefore the axes Lp of the five pistons 42 which are equidistantly placed to surround the axis Lr of the rotor 22 are located on an oval. At the start of the intake stroke, a contact point CP at which the spherical projecting portion 42 a of the piston 42 abuts against the spherical recessed portion 31 a of the swash plate 31 is located on a cross line CL on which a plane P including the center of curvature O of the spherical recessed portion 31 a and the axis Ls of the swash plate 31 intersects the spherical recessed portion 31 a.

Next, the operation of the expander E of the present embodiment with the above-described construction will be described.

The high-temperature high-pressure steam generated by heating water by a vaporizer passes through the first steam passage P1 in the steam supply pipe 85 and the second steam passage P2 of the fixed side valve plate 73, to reach the slide surface 77 of the movable side valve plate 74. The second steam passage P2 which opens to the slide surface 77 instantly communicates, in a predetermined timing, with the five third steam passages P3 formed in the movable side valve plate 74 which rotates integrally with the rotor 22, so that the high-temperature high-pressure steam passes from the third steam passage P3 through the fourth steam passage P4 formed in the rotor 22, to be supplied to the expansion chamber 43 in the cylinder sleeve 41.

Even after the communication between the second steam passage P2 and the third steam passage P3 is shut off with the rotation of the rotor 22, the high-temperature high-pressure steam expands in the expansion chamber 43, whereby the piston 42 fitted in the cylinder sleeve 41 is pushed forward from the top dead center to the bottom dead center, and the front end of the piston 42 presses the dimple 31 a of the swash plate 31. As a result, a rotation torque is given to the rotor 22 due to the reaction force which the piston 42 receives from the swash plate 31. Thus, every time the rotor 22 makes one-fifth of a turn, the high-temperature high-pressure steam is supplied into a new adjacent expansion chamber 43, thereby continuously driving the rotor 22 to rotate.

While the piston 42 having reached the bottom dead center with the rotation of the rotor 22 retreating to the top dead center by being pressed by the swash plate 31, the low-temperature low-pressure steam pushed out of the expansion chamber 43 is supplied to a condenser via the fourth steam passage P4 of the rotor 22, the third steam passage P3 of the movable side valve plate 74, the slide surface 77, the fifth steam passage P5, and the steam discharge pipe 89.

As explained in FIG. 5, when the pressure of the operating chamber 43 rises abruptly and the piston 42 is forcefully pushed out at the start of the intake stroke, the contact surface pressure between the spherical projecting portion 42 a of the piston 42 and the spherical recessed portion 31 a of the swash plate 31 abruptly rises, leading to the problem that the contact point CP between the spherical projecting portion 42 a and the spherical recessed portion 31 a slips in the circumferential direction, so that the rotational angular speed of the rotor 22 suddenly changes to cause vibration and noise. But, in the present embodiment, however forcefully the spherical projecting portion 42 a of the piston 42 may press the spherical recessed portion 31 a of the swash plate 31, the spherical projecting portion 42 a and the spherical recessed portion 31 a are prevented from slipping at the contact point CP, and the phases of the rotor 2 and the swash plate 31 are prevented from changing due to the slip, because the contact point CP at which the spherical projecting portion 42 a of the piston 42 abuts against the spherical recessed portion 31 a of the swash plate 31, is located on the arc-shaped cross line CL on which the plane P including the center of curvature O of the spherical recessed portion 31 a and the axis Ls of the swash plate 31 intersects the spherical recessed portion 31 a. As a result, the rotational angular speed of the rotor 22 is prevented from changing and causing vibration and noise, and a large side thrust is prevented from acting on the piston 42 and causing heat due to a twisting and sliding friction between the piston 42 and the cylinder 41 to cause abnormal abrasion and seizure.

It is only at the time of start of the intake stroke that the contact point CP needs to be located on the cross line CL on which the plane P including the center of curvature O of the spherical recessed portion 31 a and the axis Ls of the swash plate 31 intersects the spherical recessed portion 31 a, and in the other occasions, the contact point CP is out of the cross line CL. However, it is at the start time of the intake stroke when an impactive load is applied, that the spherical projecting portion 42 a and the spherical recessed portion 31 a are most likely to slip, and therefore a sufficient effect can be obtained.

FIGS. 7A and 7B each show the loci of movement of the contact points CP of the spherical projecting portions 42 a of the five pistons 42 by five arrows. It is understood that in the prior art shown in FIG. 7A, every time the rotor 22 rotates 72° and the intake stroke is started, the spherical projecting portion 42 a and the spherical recessed portion 31 a slip at the contact point CP, so that the movement loci of the contact points CP are discontinuous. On the other hand, in the embodiment shown in FIG. 7B, the spherical projecting portions 42 a and the spherical recessed portions 31 a are prevented from slipping, so that the movement loci of the contact points CP become continuous.

Next, a second embodiment of the present invention will be described. The rotating fluid machine of the first embodiment is an expander E using the compressible fluid as the working medium, but a rotating fluid machine of the second embodiment is a hydraulic motor using an incompressible fluid as the working medium.

As shown in FIG. 8, a second oil port P2′ which is an intake port and a fifth oil port P5′ which is a discharge port, are formed symmetrically with the top dead center TDC and the bottom dead center BDC therebetween. Accordingly, a third oil port P3′ leading to the operating chamber 43 communicates with the second oil port P2′ from a position P3′ (1) past the top dead center TDC by an angle γ to a position P3′ (2) with the angle γ before the bottom dead center BDC, during which the intake stroke is performed. As shown by the chain line in FIG. 5, the pressure of the operating chamber 43 that abruptly rises at the same time as the start of the intake stroke, is then kept at a fixed value, and abruptly lowers at the same time as the termination of the intake stroke.

In the second embodiment, at the time of start of the intake stroke when the pressure of the operating chamber 43 abruptly rises, namely, at the position P3′ (1) past the top dead center TDC by the angle γ, the contact point CP at which the spherical projecting portion 42 a of the piston 42 abuts against the spherical recessed portion 31 a of the swash plate 31 is located on the cross line CL on which the plane P including the center of curvature O of the spherical recessed portion 31 a and the axis Ls of the swash plate 31 intersects the spherical recessed portion 31 a. As a result, when the pressure of the operating chamber 43 abruptly rises with the start of the intake stroke, the spherical projecting portion 42 a and the spherical recessed portion 31 a at the contact point CP are prevented from slipping in the circumferential direction, the radial direction and the like, and the rotational angular speed of the rotor 22 is prevented from changing and causing vibration, noise, abnormal abrasion and the like.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

For example, the time at which the contact point CP is located on the cross line CL is set at the time of the start of the intake stroke in the first embodiment as well as in the second embodiment, but it can be set at an optional time when the piston 42 presses the swash plate 31.

The spherical projecting portion 42 a and the spherical recessed portion 31 a do not need to have a strict spherical surface, and they may have any spherical surface as long as the spherical surface is formed by rotating a line about an axis. 

1. A rotating fluid machine comprising: a casing; a rotor rotatably supported by the casing; an axial piston cylinder group annularly disposed in the rotor to surround an axis of the rotor; a swash plate rotatably supported on an axis inclined with respect to the axis of the rotor; and a rotary valve for controlling supply and discharge of a working medium to and from an operating chamber formed between a piston and a cylinder of the axial piston cylinder group; a spherical projecting portion formed at a tip end of the piston abutting against a spherical recessed portion annularly disposed in the swash plate to surround the axis of the swash plate; the rotor being rotationally driven by a reaction force which the spherical projecting portion of the piston receives from the spherical recessed portion of the swash plate, the piston advancing by pressure of the working medium supplied to the operating chamber, wherein a contact point at which the spherical projecting portion of the piston presses the spherical recessed portion of the swash plate is located on a cross line on which a plane including a center of curvature of the spherical recessed portion and the axis of the swash plate intersects the spherical recessed portion.
 2. The rotating fluid machine according to claim 1, wherein the contact point at a moment when the working medium is supplied to the operating chamber is located on the cross line.
 3. The rotating fluid machine according to claim 2, wherein the working medium is a compressible fluid.
 4. The rotating fluid machine according to claim 1, wherein the spherical projecting portion and the spherical recessed portion at the contact point are prevented from slipping in the circumferential direction and the radial direction.
 5. The rotating fluid machine according to claim 4, wherein a phase of the rotor and the swash plate are prevented from being displaced to cause vibration, noise and abnormal abrasion and seizure due to sliding friction and heat generation.
 6. The rotating fluid machine according to claim 2, wherein at a moment when the pressure of the working medium supplied from to the operating chamber increases, slip between the spherical projecting portion and the spherical recessed portion at the contact point is prevented.
 7. The rotating fluid machine according to claim 1, wherein the contact point wherein the spherical projecting portion of the piston abuts against the spherical recessed portion of the swash plate is an arc-shaped cross line for preventing slipping therebetween.
 8. The rotating fluid machine according to claim 7, wherein a side thrust is prevented from acting on the piston to avoid twisting and sliding friction between the piston and the cylinder to avoid abrasion and seizure.
 9. The rotating fluid machine according to claim 1, wherein the contact point is located on the cross line at the time of start of an intake stroke of the piston.
 10. The rotating fluid machine according to claim 1, wherein an axis of the rotor is inclined at a predetermined angle relative to the axis of the swash plate and wherein the piston cylinder group are located on an oval to be equidistantly positioned to surround the axis of the rotor.
 11. A rotating fluid machine comprising: a rotor rotatably supported within a casing; a plurality of pistons annularly disposed in the rotor to surround an axis of the rotor; a swash plate rotatably supported on an axis inclined with respect to the axis of the rotor; and a rotary valve for controlling supply and discharge of a working medium to and from an operating chamber formed between a piston and a cylinder of each of the plurality of pistons; a spherical projecting portion formed at a tip end of the piston abutting against a spherical recessed portion annularly disposed in the swash plate to surround the axis of the swash plate; the rotor being rotationally driven by a reaction force which the spherical projecting portion of the piston receives from the spherical recessed portion of the swash plate, as each piston advances in reaction to pressure of the working medium supplied to the operating chamber, wherein a contact point at which the spherical projecting portion of the piston presses the spherical recessed portion of the swash plate is located on a cross line on which a plane including a center of curvature of the spherical recessed portion and the axis of the swash plate intersects the spherical recessed portion.
 12. The rotating fluid machine according to claim 11, wherein the contact point at a moment when the working medium is supplied to the operating chamber is located on the cross line.
 13. The rotating fluid machine according to claim 12, wherein the working medium is a compressible fluid.
 14. The rotating fluid machine according to claim 11, wherein the spherical projecting portion and the spherical recessed portion at the contact point are prevented from slipping in the circumferential direction and the radial direction.
 15. The rotating fluid machine according to claim 14, wherein a phase of the rotor and the swash plate are prevented from being displaced to cause vibration, noise and abnormal abrasion and seizure due to sliding friction and heat generation.
 16. The rotating fluid machine according to claim 12, wherein at a moment when the pressure of the working medium supplied from to the operating chamber increases, slip between the spherical projecting portion and the spherical recessed portion at the contact point is prevented.
 17. The rotating fluid machine according to claim 11, wherein the contact point wherein the spherical projecting portion of the piston abuts against the spherical recessed portion of the swash plate is an arc-shaped cross line for preventing slipping therebetween.
 18. The rotating fluid machine according to claim 17, wherein a side thrust is prevented from acting on the piston to avoid twisting and sliding friction between the piston and the cylinder to avoid abrasion and seizure.
 19. The rotating fluid machine according to claim 11, wherein the contact point is located on the cross line at the time of start of an intake stroke of the piston.
 20. The rotating fluid machine according to claim 11, wherein an axis of the rotor is inclined at a predetermined angle relative to the axis of the swash plate and wherein the plurality of pistons are located on an oval to be equidistantly positioned to surround the axis of the rotor. 